Some related-art disc brakes include a rotation restriction mechanism (ratchet mechanism) for holding a braking force during application of a parking brake and the like in a planetary gear speed reduction mechanism (refer to Japanese Patent Application Laid-open No. 2010-169248 and Japanese Patent Application Laid-open No. 2014-92165).
However, in the disc brake disclosed in Japanese Patent Application Laid-open No. 2010-169248, a mechanism for holding the braking force is complex, resulting in a fear of a decrease in a manufacturing efficiency of the disc brake.